A semiconductor integrated circuit has become finer and more integrated in recent years. Photolithography has been frequently used as a pattern formation technology for realizing microprocessing. In addition, for example, an improvement in accuracy of an apparatus for a photolithography technology has been currently advanced. However, the photolithography technology cannot cope with a requirement of processing accuracy in an excess condition of the diffraction limit of exposure light to be used in the photolithography.
In view of the foregoing, a nanoimprint method, that enables better microprocessing has been proposed. The nanoimprint method is one kind of pattern formation technology for a thin film involving pressing a mold in which a fine irregular pattern has been formed against a substrate to which a resin thin film has been applied to transfer the irregularity of the mold onto the resin thin film applied and formed onto the substrate.
Of such nanoimprint methods, a photo-nanoimprint method introduced in, for example, Non-patent Literature 1 has been attracting attention. The photo-nanoimprint method is a method involving: imprinting a mold transparent with respect to exposure light on a photocurable composition applied onto a substrate; curing the photocurable composition by photoirradiation; and releasing the mold from the cured product to manufacture a fine resist pattern integral with the substrate.
However, several challenges to be solved arise upon utilization of the photo-nanoimprint method. One of the challenges is that a force required to release the mold from the cured product, i.e., a release force is large. In other words, the photo-nanoimprint method causes such problems as described below owing to the large release force. A defect occurs in the pattern or the substrate floats from a stage to reduce positioning accuracy between the mold and the substrate.
To cope with the challenge, Patent Literature 1 and Patent Literature 2 each propose the following method. A photocurable composition to which a gas generator that generates a gas such as nitrogen or carbon dioxide through a photoreaction has been added is used and the release force is reduced with the pressure of the gas generated by photoirradiation.
However, in the method, of Patent Literature 1, the performance of the photoirradiation results in simultaneous or competitive occurrence of the curing reaction of the photocurable composition and the gas-generating reaction. As a result, the gas is generated from the gas generator in a state where the photo-curing of the photocurable composition is insufficient. Accordingly, such a problem that a pattern defect occurs owing to a bubble or a sufficient release force-reducing effect is not obtained after the photo-curing has arisen.
It should be noted that Patent Literature 2 proposes, as a solution to the challenge of the gas generation, that the photo-curing reaction of the photocurable composition and the gas-generating reaction are performed in steps different from each other. However, the adoption of the method causes the following new challenges. The number of steps is large and productivity is low.